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The Low Activity Waste Facility will have two melters to turn waste into glass. They arrived at the plant in November 2010 and workers recently finished the complex task of assembling them.

“When operational, these melters will be the largest operating vitrification melters in the world,” said Bill Hamel, the Department of Energy project director for the plant.

The second track toward the plant’s completion is preparing to turn high-level radioactive waste into glass at separate facilities at the plant, with all facilities fully operating by a court-enforced deadline of 2036.

Construction has been stopped since 2012 at parts of the plant that will handle high-level radioactive waste until nine technical issues can be addressed.

The fourth of those issues, requiring a laboratory built at Washington State University Tri-Cities for testing, has been resolved, Hamel said Wednesday.

“It’s a great achievement,” said Alex Smith, manager of the Washington State Department of Ecology Nuclear Waste Program.

Testing in tanks the size of those that will be used at the vitrification plant’s Pretreatment Facility showed that a mixing system will be able to keep even the most challenging of the waste well mixed at the plant.

Earlier calculations had shown that a pulse jet mixing system should keep the waste well mixed, but former Energy Secretary Steven Chu ordered a full-scale test to confirm it.

The pulse jet mixers are designed to have no moving parts that would require maintenance after they start mixing radioactive waste and become contaminated. They work like a turkey baster, sucking up mostly liquid waste within the tank and then expelling it, mixing the waste in the process.

Testing started in 2014 at what is now called the Atkins Engineering Laboratory at WSU Tri-Cities.

It showed that waste that may include heavy particles of plutonium and may have the consistency of peanut butter can be kept mixed well enough to keep the treatment system operating. If some waste settles out it could pose a risk of an uncontrolled nuclear reaction or a buildup of flammable hydrogen.

The remaining four technical issues are expected to be resolved by the end of the year.

“The key to protecting the (Columbia) River is vitrifying the 56 million gallons of waste in those tanks here at Hanford,” Smith said at an event announcing the final assembly of the melters Wednesday.

Hanford vitrification plant workers place wooden 4-by-4-inch blocks over steel rods as protection while they finish work on the glass-melter lids.

Courtesy Bechtel National

Construction on the Low Activity Waste Facility should be finished by June 2018, after significant progress was made this year, said Peggy McCullough, vit plant project director for contractor Bechtel National.

Assembling the melters was a particularly complex task, Hamel said.

The inside surface of each melter is a refractory made of a layer of hundreds of interlocking bricks of different sizes and shapes that must fit within a 16th of an inch tolerance, Hamel said.

When the melter gets hot, the refractory will expand and form a seal.

The refractory is surrounded with a metal shell with a bolt system to keep it from expanding or contracting too much, then a cooling jacket and another shell.

Each melter also has a system of lids, with one serving as a radiation shield and the other sealing the melter to allow a ventilation system to keep radioactive gases contained.

Within the melters, concentrated low-activity radioactive waste will be mixed with glass-forming materials, including silica, and then heated to 2,100 degrees Fahrenheit. The mixture will be poured into stainless steel containers to harden for permanent disposal at Hanford.

When operational, these melters will be the largest operating vitrification melters in the world.

Bill Hamel, Department of Energy project director for the plant

The melters are 10 times larger than the melters being used to process high-level radioactive waste at DOE’s cleanup site at Savannah River, S.C., McCullough said.

Each of the Hanford Low Activity Waste Facility’s melters weigh 300 tons and measure 20 by 30 feet and 16 feet high. Together they will produce 30 tons of glass a day.

Bechtel National earned $4.275 million, as outlined in its contract, for getting the first melter assembled earlier this year. It is due another $4.275 million for assembling the second one.

Construction work still to be done at the facility includes installing electrical equipment and permanent lighting and hooking up mechanical equipment.

When construction is completed, systems — electrical, water, mechanical, steam and chillers — will be started up, first as individual components, then at the system level and then facility wide.

That will be followed by commissioning. Vitrification processes will be tested first with water and then with mock waste before the plant begins treating radioactive waste by a planned date of 2022.